The present invention pertains to data transmission and reception between telecommunications switching systems via digital spans and more particularly to a digital phase locking arrangement for synchronizing the reception of digital span data.
In telecommunications switching, it is necessary to send large amounts of data between switching offices. To efficiently accomplish this result, high speed data link between these switching offices have been developed. These high speed data links are termed T-carrier transmission facilities. For example, these T-carrier transmission facilities include T-1, T-2, etc. digital span line equipment, which provide data at high speed in data formats DS-1 or DS-2, respectively.
Modern telecommunications switching offices handle communications between a number of different sources. Thereby, the switching office is required to handle a number of different digital spans. These digital spans transmit their data asynchronously with respect to one another. The switching office requires data reception circuitry for each of its digital span units. Due to the asynchronous transmission of the digital spans, a master clocking arrangement is ineffective to enable data reception for a number of digital spans.
In addition, high speed signals drift over a period of time.
Accordingly, it is the object of the present invention to provide an efficient and small in size digital phase locking arrangement for synchronizing the reception of high speed digital span data.